The unpublished report by Jim Gamble, former head of the Child Exploitation and Online Protection Centre (CEOP), found that so many UK agencies got involved, it damaged relations with Portuguese police.

The report, commissioned by former UK Home Secretary Alan Johnson in 2009, was delivered in 2010 and led to the Metropolitan Police reopening the probe into Madeleine's disappearance, but was never released.

For the first time, details have been given to Sky News, revealing that Mr Gamble criticised the Association of Chief Police Officers' decision to put Leicestershire Police in charge of the operation because the McCanns lived in the county, despite the fact that the force was ill-equipped to deal with such a big investigation.

Mr Gamble said that within weeks of Madeleine going missing in May 2007, the Portuguese were given advice by CEOP, the Metropolitan Police, the Serious Organised Crime Agency and the National Police Improvement Agency.

The Crimestoppers charity published its own appeal hotline and different government ministers - No 10, the Home Office and the Foreign Office - were demanding briefings from the various agencies.

Mr Gamble said: "All of us, including myself at CEOP at the time, your first gut reaction is you want to help, a child has gone missing … so everyone came with best intentions, that created a sense of chaos and a sense of competition, people putting their hand up and wanting to help and in many instances in my opinion wanting to be seen to help.

"If we look at it honestly there were some in leadership roles who wanted to represent their organisation to be seen to take a lead role and be seen to provide critical input in this and that made it difficult for a small, regional force like Leicestershire.

"It was unhelpful … I've no doubt relationships from the outset with the Portuguese were impacted by it and I think that had a long-term negative effect on the investigation and I think to this very day the Met investigation team that's engaged now are still having to manage that relationship now."